Laminated article



Patented Mar. 1, 1938 LAMINATED Aa'rrcnn John W. Haught, Arlington, N. 1., assignonby mesne assignments, to E. I. du Pont de Ne- Wilmingto mours & Company, poration of Delaware n, M, a eor- No Drawing. Application December 7, 19:5,

Serial No. 53,425

2C'lalms.

This invention relates to laminated articles and, more particularly, to laminated glass, i. e., safety glass, and the composition of the interlayer sheeting used therein. The invention is 5 concerned with interlayer compositions compris ing cellulose nitrate.

Heretofore, it has not been possible to obtain interlayer sheeting of a cellulose nitratecomposition which, when used as an interlayer in safety glass, does noteither develop bubbles on short exposure to sunlight or become brittle whe'nsuhjected to winter temperatures.

An object of the present invention is to pro-- vide interlayer sheeting for use in safety glass,

'15 and the like, comprising cellulose nitrate,

which sheeting is of good strength and toughness and retains this desirable strength and toughness over the range of temperatures 01' use of safety glass. A further object is to provide an inter-layer sheet which. when used in safety glass or similar laminated articles, does not develop bubbles under ordinarily severe conditions of service and is not susceptible to appreciable disooloration by sunlight. Other objects of the g5 invention will be. apparent from the description given hereinafter.

The above objects are accomplished according to the present invention by the use of an interlayer sheet for safety glass and other laminated articles comprising 100 parts of cellulose nitrate and 80-120 parts of a plasticizer therefor comprising a dialhl hexahydrophthalate in which each alkyl group contains from 4-10 carbon atoms, inclusive. More specifically. it is preferred to use the plasticizer in the proportion of 90- 100 parts'to 100 parts of'cellulose nitrate. Parts aregiven throughout the specification and claims by weight.

The dialkyl hexahydrophthalates are limited 40 to those wherein each albl group contains from (-10 carbon atoms, inclusive. because when the alkyl group contains less than 4 carbon atoms an interlayer sheet results which, in safety glass, and the like, will develop bubbles after short exposure to sunlight. on the other hand, when the slim] group contains more than 10 carbon atoms, the colloiding action 'on'cellulose nitrate of the ester is too weak to give an lnterlayer sheet which can be satisfactorily bonded to glass.

In the small class of dialhl hexahyrlrophtha.-

lates coming within the scope of the present invention. the solvent or plasticixing strength with respect to cellulose nitrate decreases with increaselnthesileofthe alkylradical. Fbrexample, the dibutyi, dianrvl, and dihexyl hexahydrophthalates may be used as sole plasticizers with excellent results, whereas the diheptyl, dioctyl, dinonyl, and didecyl hexahydrophthalates are preferably used in admixture with other plastb 5 cizers of somewhat greater plasticizing activity such as the lower members of the herein considered group of hexahydrophtha'lates, and diamyl phthalate, dimethylcyclohexyl adipate, or diamyl succinate. The proportions of the more 10 active plasticizers will, in general, be larger with increase in the number of carbon atoms in the alkyl group of the dialhl hexahydrophthalate employed and may range from about 10% to about by weight of the total plasticizer mix- 15 tures.

Mixtures of the hexahydrophthalates may be used toadvantage and among such mixtures a particularly advantageous one is obtainedby es- 'terifying a mixture of alcohols, both straight and 20 branched chain, arising as by-products in the synthesis of methanol. The .esterification of this mixture gives an ester mixture consisting essentially of dihexyl, diheptyl, and dioctyl hexahydrophthalates. The esters of both cisor transhexahydrophthalic acid, or mixtures of them, may be used interchangeably in the present invention.

The following examples are given in order tO- illustrate specific embodiments of the present invention:

Example 1 A composition consisting of:

Parts Cellulose nitrate Diamyl hexahydrophthalate- 93 Denatured alcohol 76 was made up by colloiding the ingredients in a Werner-Pfieiderer mixer, filtered by hydraulic pressure through heavy muslin, rolled to remove excess solvent, consolidated by heat and pressure, and from the resulting block sheets of approximately 0.020" caliper were sliced. These sheets were seasoned, i. e., treated to remove substantially all of the volatiles but no substanial part of the plasticizer. A sheet thus treated was laidbetween two glass plates previously coatedwith an adhesive and subjected to a temperature of about 185 C. and a pressure of pounds per square inch. 4

. Inthe following examples merely the composition of the interlayer sheet is given Since the procedure was substantially identical with that set forth in Example 1:

Example 2 Parts Cellulose nitrate 100 Mixed hexahydrophthalates 93 Denatured alcohol 76 The mixed hexahydrophthalates were substantially a mixture of isomeric dihexyl, diheptyl, and dioctyl hexahydrophthalates obtained by esterifying a mixture of alcohols obtained as by products in the synthesis of methanol. t

Example 3 Parts Cellulose nitrate 100 Mixed hexahydrophthalates 80 Diamyl phthalate 17 Denatured alcohol 76 The mixed hexahydrophthalates were the same as those used in Example 2.

was colloided and filtered and the resulting colloid was extruded by customary means known in the art in the form of a wide ribbon through an orifice. The balance of the treatment was similar to that set forth in Example 1. The mixed I hexahydrophthalates'were the same as used in Example 2.

The following examples illustrate suitable interlayer sheeting compositions adapted to be worked up according to either the procedure in Example 1 or Example 6:

Example 7 Parts Cellulose nitrate 100 Diamyl phthalate 48 Dinonyl hexahydrophthalate 35 Example 8 Parts Cellulose nitrate 100 -Dibutyl hexahydrophthalate 7 Example 9 Parts Cellulose nitrate Diamyl phfhalafe 10 Dihexyl hexahydrophthalate 80 It will be understood that the above examples are merely illustrative and that the present invention broadly includes within its scope the use of an interlayer sheet comprising 100 parts of cellulose nitrate and 80-120 parts of a plasticizer therefor comprising a dialkyl hexahydrophthalate wherein each alkyl group contains from 4-10 carbon atoms, inclusive, in laminated glass or similar articles. The present invention is useful in laminating sheets of other brittle material, as well as sheets of glass, although the use of the present invention with respect to laminated or safety glass is of the greatest importance. As will be understood by those skilled in the art, the laminated glass may comprise merely a single sheet of glass and a single interlayer sheet, or two sheets of glass united by an interlayer sheet, or a plurality of sheets of glass united by a pluralityof interlayer sheets.

The invention is entirely independent of the method of preparing the interlayer sheets. Any of the known methods may be used which will serve to produce interlayer sheeting which meets the ordinary strict standards of the art as re gards cleanness, clearness, correctness of color, uniformity of thickness, and the like. Likewise, the invention is independent of the manner in which the interlayer sheet is bonded to the glass to form the laminated article. Interlayer sheets made according to the present invention can be satisfactorily bonded to glass by any of the standard methods already established, preferably with the use of adhesive.

An advantage of the present invention is that the interlayer sheets produced in accordance therewith have excellent strength and toughness and retain this strength and toughness over the entire temperature range to which safety glass is normally subjected. The sheeting is not appreciably embrittled by' winter temperatures nor is it subject to cold flow at summer temperatures. Moreover, this interlayer sheeting, when used in safety glass, does not develop bubbles under ordinarily severe conditions of service and is entirely satisfactory from the standpoint of discoloration by sunlight.

As many apparently widely diflferent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

I claim:

1. Laminated glass comprising a sheet of glass and, bonded thereto, a plastic sheet comprising 100 parts of cellulose nitrate and about 85 parts of dibutyl hexahydrophthalate.

2. Laminated glass comprising a sheet of glass and, bonded thereto, a plastic sheet comprising 100 parts of cellulose nitrate and 80-120 parts of a diakyl hexahydrophthalate wherein each alkyl group contains from 4-6 carbon atoms, inclusive.

JOHN W. HAUGHT. 

